The Empirical Relationship Between Water Saturation and Seismic Wave Attenuation in Unconsolidated Sand
Jie Shen
Louisiana
State
University,
Department
of
Geology
and
Geophysics,
Baton
Rouge,
LA,
USA
[email protected]
Compressional (P) and shear (S) waves have long been used to study the subsurface. However, current constitutive models and fluid-substitution models derived from hard-rock cases do not properly predict seismic velocities in water saturated unconsolidated sand. The current empirical model for explaining seismic wave attenuation as a function of water saturation in sandstone does not fit data for unconsolidated sand. While P-wave and S-wave velocity analysis can teach us much about the elastic properties of soils, seismic attenuation can tell us much about the inelastic properties of the pore fluids. I seek to use the attenuation of seismic P- waves and S-waves to determine water saturation in unconsolidated sand. I collect P-wave and S-wave data, varying water saturation in a sand filled tank that can be filled with water to any depth desired. I also deploy moisture meters to directly measure water saturation in unconsolidated sand. From the experimental data, I extract the seismic wave attenuation for different water saturations and determine the empirical relationship between the seismic wave attenuation and water saturation in unconsolidated sand. The results should be applied to estimate water saturation seismically in unsaturated unconsolidated sand and carry implications for reservoir characterization, soil evaluation and contamination remediation. Understanding seismic characterization of unconsolidated sediments will provide information on soils and related geological environments for interpretation of seismic measurements in sediments.
AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects